Best chance for a 269 to 269 Tie in the Electoral College?

[True Federalist (진정한 연방 주의자)]

So, this basically ends in Romney/Biden?

Most hilarious four years ever!

With the current House and Senate it would end Romney/Biden, but it'll be the 113th Congress that gets to break a tie.

Assuming a straight party-line vote with everyone present, the current House would vote:

Romney: 33
 AL, AK, AZ, AR, CO, FL, GA, ID, IL, IN,
 KS, KY, LA, MI, MS, MO, MT, NE, NV, NH,
 ND, OH, OK, PA, SC, SD, TN, TX, UT, VA,
 WV, WI, WY

Obama: 15
 CA, CT, DE, HI, IA, ME, MD, MA, NM, NY,
 NC, OR, RI, VT, WA

abstain: 2
 MN, NJ

The GOP has enough states that it is conceivable that they could lose control of the House in November and yet still control a majority of the delegations and thus be able to elect Romney with a tied electoral college.  However, I can't see the GOP losing control of the House if the electoral college is tied.  They might even gain seats and delegations.

The Senate is more fun.  A 269-269 EV tie and a 50-50 Senate tie is certainly possible and would mean no Vice President unless someone broke party ranks.

Of the four scenarios presented, #2 is most likely, and #3 is the least likely.

[True Federalist (진정한 연방 주의자)]

Yes, it's safe to assume that if there's an electoral tie, the Republicans will have more state delegations in the House, and so Romney wins there. As for the Senate, a 50/50 tie would have Biden break the tie for himself.

Biden won't get to break that tie if it occurs. It requires a majority of the whole number of Senators to elect a Vice President, so it takes 51 Senators to elect a Vice President, not 50-50 with the sitting VP breaking a tie, nor 50-49 if one of them doesn't vote.

[True Federalist (진정한 연방 주의자)]

so how would a tied senate operate? Someone would be expected to cross over to whichever party won the popular vote?

Biden would still be Vice President for the first 17 days of the Senate being in session, so the Democrats would get to organize the Senate.  But if neither side is willing to compromise, then we'd likely not have a Vice President for a couple of years.  It's not really a major problem, especially since the Speaker would be of the same party as the President, so if something did happen to Romney, a Republican would succeed him.

Personally, I think some sort of compromise would happen, probably to have the PV winner hold the bucket of spit, but maybe coupled with a constitutional amendment being sent to the states to eliminate the electoral college.

[True Federalist (진정한 연방 주의자)]

In such a scenario, would the election actually go to the House/Senate though? Wouldn't quasi-constitutional deal-making, along with political and legal maneuvering before the Electoral College votes be more likely?

There is no reason for a deal involving the electors.  In any plausible scenario that produces an EV tie in 2012, the GOP will control 26 or more state delegations in the House and thus be able to elect Romney outright.  The need to worry about the Vice-Presidential election only arises if the Senate is split 50-50 and under the circumstances, with the next in line being the Republican Speaker, there is no urgent reason beyond how it looks for either side to compromise.

Plus to reach a deal involving the electors, you'd need not only a pair of Republicans and Democrats to agree to vote the same for President and Vice President to determine the election, you'd have to worry that some other joker might decide to play faithless elector as well and ruin the deal.

Given the composition of the House, the real fun scenario is what if a faithless elector decides to vote for neither Obama or Romney for President, but for someone else such as Paul Ryan, Ron Paul, Tim Scott, etc.  If the Republicans take the Senate so that a Republican Vice President will be in place if the House fails to elect a President, Romney might be denied the presidency after all as the House votes from among the top 3.  (Not that I think it a likely scenario, as I doubt the House would rise to the bait, but Romney might have to make some concessions to the nuts in his party to be sure of winning.)

[True Federalist (진정한 연방 주의자)]

The new congress would probably get to make the pick, but this isn't nearly as certain as people like to pretend. Originally under the 12th amendment it was the outgoing congress that got to break an electoral college deadlock. The 20th amendment changed the start dates of terms and  placed the start of the new congress before the start of the new president's term which implies that it would today be the incoming congress that would choose the president, but this isn't explicitly laid out anywhere in the constitution. Current federal law mandates that the electoral votes are counted before a joint session of congress on January 7 (4 days after the new congress takes power), but theoretically the outgoing congress could just pass a bill to move the counting of electoral votes up to December right after the electors meet. The outgoing House could then proceed to the election of the president. If Republicans were to lose the House in November, you could potentially have a nasty legal battle/constitutional crisis over which House gets to choose the president.

While theoretically a lame duck Congress could move up the date of a Congressional election to decide the Presidency, Vice Presidency, or both, as a practical matter, they couldn't do it with the current Congress as the Senate would never agree to such a change, and even if they could, such shenanigans would be political poison.

[True Federalist (진정한 연방 주의자)]

What's the Obama 270 map?

Here's a possible Obama 270 map.

[True Federalist (진정한 연방 주의자)]

Ok, if the Senate was 50/50 then yes, obviously the Democrats would elect Biden as VP in order to preserve control of the Senate. But otherwise isn't it somewhat likely that at least a couple Democratic Senators would make the political calculation that there just aren't that many points to be scored in the eyes of the public by electing a Democratic VP just to screw with the incoming Republican President?

As I already pointed out, it there is a 50-50 tie in the Senate, then neither party can elect a Vice President on its own.  It takes a majority of the whole number of Senators to elect a Vice President.  Biden can't break the tie on his own, and a Senator can miss a vote without having to worry that his absence will cause the election of someone he doesn't want to be elected.  A 50-49 vote can't elect a VP either.

[True Federalist (진정한 연방 주의자)]

If this EV tie occurs, it is most likely that the GOP will control >=26 state delegations in the House and elect Romney.  In the Senate, if there is a 50-50 tie, I would expect a filibuster to stop a vote.  Then, after Romney were inaugurated, I suspect he would nominate a VP to fill the vacancy under the 25th Amendment.  That could lead to all kinds of legal arguments and with a tied Senate and no VP to break ties, it would be very messy.  Probably a compromise would occur but who knows what it would be!

There is no need to filibuster with a 50-50 tie.  It takes 51 to elect a Vice President.  I also can't see either party filibustering if the Senate is not tied, as it would be political poison.  Going the 25th Amendment route wouldn't make things easier.