Would it be possible for someone to pull off a reverse Arlen Specter?

[America Needs a 13-6 Progressive SCOTUS]

Basically, Arlen Specter was in this situation with these 2 choices for the 2010 election:

Remain a Republican and then lose the Republican primary to Pat Toomey.
Switch to the Democrats and then lose the Democratic primary to Joe Setsak.

Basically, he was inevitably going to lose renomination regardless of whether he switched parties and tried to win the nomination for the new party or if he simply remained in the same party and tried to win the nomination for that party again.

For someone to pull off a reverse Arlen Specter, it would mean that they have to get in this situation:

They could feasibly switch parties and then win the primary in their new party.
They could feasibly remain in their current party and then win the primary in their current party.

I would imagine getting into that situation would be quite difficult, but would it even be possible for anyone to pull that off?

[SteveRogers]

Lisa Murkowski, theoretically.

[Torrain]

Lisa Murkowski, theoretically.

Her 2010 and 2016 are pretty close to the hypothetical stated by OP

[gerritcole]

manchin

[I spent the winter writing songs about getting better]

Collin Peterson

[Amenhotep Bakari-Sellers]

Collins needs to run as an indie like Murkowski, she doesn't fit in with the GOP

[Fuzzy Bear]

Collins could become a Democrat and win the primary.

Murkowski is a worse fit for the Democrats, but it's possible that Alaska Democrats would be willing to make an accommodation and accept her as a convert.

[AudmanOut]

Collins could become a Democrat and win the primary.

Murkowski is a worse fit for the Democrats, but it's possible that Alaska Democrats would be willing to make an accommodation and accept her as a convert.

Are you kidding me? In my opinion murkowski is a much better fit for the dems then Susan Colins is.

[Dr Oz Lost Party!]

Collins could become a Democrat and win the primary.

Murkowski is a worse fit for the Democrats, but it's possible that Alaska Democrats would be willing to make an accommodation and accept her as a convert.

Are you kidding me? In my opinion murkowski is a much better fit for the dems then Susan Colins is.

Yeah, especially after her Kavanaugh grandstanding.

[BundouYMB]

Collins could become a Democrat and win the primary.

Murkowski is a worse fit for the Democrats, but it's possible that Alaska Democrats would be willing to make an accommodation and accept her as a convert.

Are you kidding me? In my opinion murkowski is a much better fit for the dems then Susan Colins is.

Yeah, especially after her Kavanaugh grandstanding.

Collins is spinless. Bought and paid for. The Republicans can keep her.

Murkowski is pretty conservative, but she's pro-choice and votes her state. She's not a hack, and she's not in anyone's pocket. If we needed her to get to 51, I'd be willing to accept Murkowski joining the party.

[Fuzzy Bear]

Collins could become a Democrat and win the primary.

Murkowski is a worse fit for the Democrats, but it's possible that Alaska Democrats would be willing to make an accommodation and accept her as a convert.

Are you kidding me? In my opinion murkowski is a much better fit for the dems then Susan Colins is.

Let's look at ADA ratings over time:

2016:  Murkowski 15, Collins 45

2015:  Murkowski 25, Collins 30

2014:  Murkowski 30, Collins 35

2013:  Murkowski 30, Collins 50

2012:  Murkowski 35, Collins 50

2011:  Murkowski 40, Collins 45

2010:  Murkowski 20, Collins 40

2009:  Murkowski 35, Collins 65

2008:  Murkowski 25, Collins 75

2007:  Murkowski 30, Collins 55

2006:  Murkowski   5, Collins 45

2005:  Murkowski 20, Collins 65

2004:  Murkowski 35, Collins 45

2003:  Murkowski 20, Collins 45

On average, Collins is slightly over 23 points higher per year on ADA's LQ ("Liberal Quotient"). 

People have this idea that Murkowski is some kind of moderate Republican, while Collins is really a conservative.  This perception, IMO, is driven by a combination of (A) Murkowski's vocal opposition to Kavanaugh's confirmation in comparision to Collins' support for Kavanaugh, (B) Murkowski's successful opposition to Tea Party Republican Joe Miller in 2010, and (C) the fact that the arch-enemy of the Murkowski family is Sarah Palin (who defeated Frank Murkowski in the 2006 GOP Gubenatorial primary).  This conception simply does not stand up in the face of the numbers.  Collins is a moderate Republican who could credibly switch parties and possibly win a Democratic Primary by making accomodations on a few issues.  Murkowski does not have the kind of record that, over time, would make a switch to the Democratic Caucus credible, even if she were to become an Independent and caucus with the Democrats.  If she became an Independent and caucused with the GOP, she would be credible, but it would not be easy for her to win the GE under those conditions.

[BundouYMB]

Collins could become a Democrat and win the primary.

Murkowski is a worse fit for the Democrats, but it's possible that Alaska Democrats would be willing to make an accommodation and accept her as a convert.

Are you kidding me? In my opinion murkowski is a much better fit for the dems then Susan Colins is.

Let's look at ADA ratings over time:

2016:  Murkowski 15, Collins 45

2015:  Murkowski 25, Collins 30

2014:  Murkowski 30, Collins 35

2013:  Murkowski 30, Collins 50

2012:  Murkowski 35, Collins 50

2011:  Murkowski 40, Collins 45

2010:  Murkowski 20, Collins 40

2009:  Murkowski 35, Collins 65

2008:  Murkowski 25, Collins 75

2007:  Murkowski 30, Collins 55

2006:  Murkowski   5, Collins 45

2005:  Murkowski 20, Collins 65

2004:  Murkowski 35, Collins 45

2003:  Murkowski 20, Collins 45

On average, Collins is slightly over 23 points higher per year on ADA's LQ ("Liberal Quotient").  

People have this idea that Murkowski is some kind of moderate Republican, while Collins is really a conservative.  This perception, IMO, is driven by a combination of (A) Murkowski's vocal opposition to Kavanaugh's confirmation in comparision to Collins' support for Kavanaugh, (B) Murkowski's successful opposition to Tea Party Republican Joe Miller in 2010, and (C) the fact that the arch-enemy of the Murkowski family is Sarah Palin (who defeated Frank Murkowski in the 2006 GOP Gubenatorial primary).  This conception simply does not stand up in the face of the numbers.  Collins is a moderate Republican who could credibly switch parties and possibly win a Democratic Primary by making accomodations on a few issues.  Murkowski does not have the kind of record that, over time, would make a switch to the Democratic Caucus credible, even if she were to become an Independent and caucus with the Democrats.  If she became an Independent and caucused with the GOP, she would be credible, but it would not be easy for her to win the GE under those conditions.

The problem with those rankings is that not every vote is equally important. Every time her vote might actually change something, Collins buckles and votes with her party. If she votes "liberally" on a bunch of minor bills and obscure amendments, it doesn't really matter compared to the big votes. Murkowski is willing to buck her party on the big votes. She'll stand with Democrats, occasionally, when it actually matters. That would make me at least open to considering letting Murkowski join the party, even though I do agree Murkowski is pretty darn conservative.

I would rather be in the minority than accept Collins.

[lfromnj]

It's also cleat collin can afford to shift right as maine shifted right.

[Fuzzy Bear]

Collins could become a Democrat and win the primary.

Murkowski is a worse fit for the Democrats, but it's possible that Alaska Democrats would be willing to make an accommodation and accept her as a convert.

Are you kidding me? In my opinion murkowski is a much better fit for the dems then Susan Colins is.

Let's look at ADA ratings over time:

2016:  Murkowski 15, Collins 45

2015:  Murkowski 25, Collins 30

2014:  Murkowski 30, Collins 35

2013:  Murkowski 30, Collins 50

2012:  Murkowski 35, Collins 50

2011:  Murkowski 40, Collins 45

2010:  Murkowski 20, Collins 40

2009:  Murkowski 35, Collins 65

2008:  Murkowski 25, Collins 75

2007:  Murkowski 30, Collins 55

2006:  Murkowski   5, Collins 45

2005:  Murkowski 20, Collins 65

2004:  Murkowski 35, Collins 45

2003:  Murkowski 20, Collins 45

On average, Collins is slightly over 23 points higher per year on ADA's LQ ("Liberal Quotient").  

People have this idea that Murkowski is some kind of moderate Republican, while Collins is really a conservative.  This perception, IMO, is driven by a combination of (A) Murkowski's vocal opposition to Kavanaugh's confirmation in comparision to Collins' support for Kavanaugh, (B) Murkowski's successful opposition to Tea Party Republican Joe Miller in 2010, and (C) the fact that the arch-enemy of the Murkowski family is Sarah Palin (who defeated Frank Murkowski in the 2006 GOP Gubenatorial primary).  This conception simply does not stand up in the face of the numbers.  Collins is a moderate Republican who could credibly switch parties and possibly win a Democratic Primary by making accomodations on a few issues.  Murkowski does not have the kind of record that, over time, would make a switch to the Democratic Caucus credible, even if she were to become an Independent and caucus with the Democrats.  If she became an Independent and caucused with the GOP, she would be credible, but it would not be easy for her to win the GE under those conditions.

The problem with those rankings is that not every vote is equally important. Every time her vote might actually change something, Collins buckles and votes with her party. If she votes "liberally" on a bunch of minor bills and obscure amendments, it doesn't really matter compared to the big votes. Murkowski is willing to buck her party on the big votes. She'll stand with Democrats, occasionally, when it actually matters. That would make me at least open to considering letting Murkowski join the party, even though I do agree Murkowski is pretty darn conservative.

I would rather be in the minority than accept Collins.

ADA's LQ is based on 20 significant pieces of legislation.  Neither one of these is all you'd want if you're a Democrat, but Collins is the kind of politician that is a party loyalist.  I believe that she'd be a stalwart Democrat if she switched.

Murkowski is a conservative in the John McCain mold; a conservative who's not a "movement conservative".  Collins is a moderate Republican in the New England Republican mold.

[Dr Oz Lost Party!]

Collins could become a Democrat and win the primary.

Murkowski is a worse fit for the Democrats, but it's possible that Alaska Democrats would be willing to make an accommodation and accept her as a convert.

Are you kidding me? In my opinion murkowski is a much better fit for the dems then Susan Colins is.

Yeah, especially after her Kavanaugh grandstanding.

Collins is spinless. Bought and paid for. The Republicans can keep her.

Murkowski is pretty conservative, but she's pro-choice and votes her state. She's not a hack, and she's not in anyone's pocket. If we needed her to get to 51, I'd be willing to accept Murkowski joining the party.

Tbf, she's slightly more liberal than Manchin.

[OSR stands with Israel]

Shelby did it

[Kodak]

Shelby did it

Ben Campbell did it most recently, although Shelby is still serving in the Senate.

Jim Justice could do it if he runs as a Republican in 2020.

[Fuzzy Bear]

Shelby did it

Shelby, however, was an extremely conservative Democrat; the most conservative Democrat in the Senate at the time of his switch.  If Shelby had stayed a Democrat, he likely would have been Gore's running mate in 2000.