In a fantasy multiparty system, which party would you join?

[Greedo punched first]

Which of these 12 hypothetical parties?
1. Democratic (establishment neoliberal Democrats)
2. Republican (Reagan Republicans)
3. Libertarian (right-libertarian)
4. Constitution (paleoconservative Tea Partiers)
5. Green (environmentalist social democratic)
6. Social Democratic Party (Bernie Sanders social Democrats, Trotskyists, and Eugene Debs socialists)
7. National Populist Party (Donald Trump populist conservatism)
8. Communitarian (fiscally liberal and socially conservative; socially conservative Democrats and fiscally liberal Republicans; pro-labor union; pro-life; Joe Manchin, Bob Casey, Ben Nelson, Dan Boren, and Joe Donnelly Democrats; Rick Santorum and Mike Huckabee Republicans; I named this fantasy party "Communitarian" instead of "Christian Democrats" to be more inclusive of non-Christian communitarians)
9. Knights Party (white nationalist party; David Duke types)
10. Feminist Democrats (feminist social democratic party; similar to the Social Democratic Party, but more appealing to Tumblr/third wave feminists)
11. Centrist Conservatives (moderate center-right Republicans like Brian Sandoval and some Blue Dog Democrats similar to the late Arlen Specter)
12. Tea Party (hard-right Rand Paul/Ted Cruz/Dana Rohrabacher Tea Party Republicans)

[Greedo punched first]

Centrist Conservatives

[Greedo punched first]

1. Independent
2. Centrist Conservative
3. Republican/Democratic/Libertarian

Would these be the tickets?:
Republican: Marco Rubio/Kelly Ayotte
Democratic: Martin Heinrich/Kirsten Gillibrand
Libertarian: Ron Wyden/Rand Paul
Centrist Conservative: Brian Sandoval/John Kasich

Rubio/Ayotte would be Republican. Heinrich/Gillibrand would be Democratic. Wyden/Paul is an odd ticket, definitely not Libertarian; Wyden would be Democratic, and Paul would be a libertarian-leaning Tea Party candidate. Sandoval/Kasich is definitely Centrist Conservative.

[Greedo punched first]

What other parties would you caucus with to form a coalition?

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Not a single socialist party in OP?

The socialist parties I listed are, Social Democrats, Greens, and Feminist Democrats. Which one would you join? Which parties other than the one you would join would you form a coalition with?

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FemDem if it's split roughly evenly, would consider tactically being a Dem if D and R are the two major parties and the other 10 are minor.

D and R are the two major parties. Not all Democrats would necessarily be part of the same coalition. Some Democrats might caucus with Social Democrats, Feminist Democrats, and Greens. Other Democrats might caucus with Communitarians. Other Democrats might caucus with Centrist Conservatives and Libertarians. Some Republicans would be in a coalition with Constitution and Tea Party, while others might be in one with Libertarians and Centrist Conservatives; while others might caucus with the National Populists. I would mostly vote for Centrist Conservatives, but every now and then for Libertarians and Republicans.

[Greedo punched first]

Who actually dared to make the insane choice of Knights Party?

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I would be a Centrist Conservative who caucuses with other members of my party, some Republicans and some Libertarians.

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No party for me. I'm in favor of the Communitarians, but Santorum and Huckabee disgust me. Boring old democrat, I guess, but very reluctantly.

Communitarians have a large tent, the Huckabee/Santorum wing is the party's right wing, the Joe Manchin/Dan Boren/Ben Nelson wing is the party's moderate wing, and the Donnelly/Casey wing is the party's left wing. Would you be fine with joining the Casey/Donnelly or Boren/Manchin/Nelson wing? You can be in the Communitarian Party and not caucus with the Huckabee/Santorum wing if you like. For example, Washington State Legislature member Tim Sheldon is a Democrat, but he caucuses with the Republicans.

[Greedo punched first]

1. Independent
2. Centrist Conservative
3. Republican/Democratic/Libertarian

Would these be the tickets?:
Republican: Marco Rubio/Kelly Ayotte
Democratic: Martin Heinrich/Kirsten Gillibrand
Libertarian: Ron Wyden/Rand Paul
Centrist Conservative: Brian Sandoval/John Kasich

Rubio/Ayotte would be Republican. Heinrich/Gillibrand would be Democratic. Wyden/Paul is an odd ticket, definitely not Libertarian; Wyden would be Democratic, and Paul would be a libertarian-leaning Tea Party candidate. Sandoval/Kasich is definitely Centrist Conservative.

Wyden and Paul are left-libertarian and right-libertarian, respectively. I was seeing the extent of the libertarian coalition.

The Libertarian party would be right-libertarian, like Gary Johnson. Wyden would only fit into the Democratic Party. Rand Paul would be closer to this, but he would be in the libertarian-leaning wing of the Tea Party. The left wing of the Libertarian Party would be comprised of pro-choice, pro-gay marriage, pro-gun, anti-Affordable Care Act conservative Democrats (who oppose a flat tax, but are still staunch fiscal conservatives who oppose high taxation, liberal spending, and a large welfare state); well to the right of Wyden, who wouldn't fit into this party (especially because he supports the ACA and gets an F rating from the NRA).

[Greedo punched first]

The system laid out in the OP wouldn't last for any appreciable time; you have too many parties that are basically the same thing (SDP/Feminists) or which have a base that is tiny to the point where they'd only get in to the legislature if America adopted a Dutch-style thresholdless List PR system or where the people who you've tapped as being in it wouldn't create their own party but run in one of the bigger ones.

An American multi-party system would be the sort to retain two broad church left/right parties: perhaps with the far left in a more openly socialist party and the Republicans would probably fragment in a similar way as well (in the past I'd have said that the populist element might have formed into its own party but now it makes more sense to consider that your "TRUE CONSERVATIVE!!!" elements (like Kasich or Cruz - different wings of the parties but broadly similar economically) might form a splitter party.  Additionally a multi-party system would probably lead to a much higher use of party whips and a great deal more party unity than is typical in American politics currently since the continual rebel would be chucked out, or would leave and join someone else instead.  That's why talk of being in the same party as someone but not "caucusing" with them is stupid in a multi-party system: in any voting system where you'd have six or seven parties the party that had the likes of Santorum and Casey in it would split really very quickly - and besides, what's the point of voting for a party if you don't know exactly who they are going to support in the legislature (again for this system to be viable you'd need to have list PR: and even in an Open List even when you vote only for candidates on the list that you like you have to support the entire list); especially if they'd end up divided.

A multi-party system probably would be very similar to now really: you'd have two big parties (we'll call them the Democrats and the Republicans for ease of this analogy) although the left of the Democrats probably would form a more openly Socialist party.  The Republicans would probably split as well tbh; although exactly what that split would be is more complicated (in the past I'd have said that you'd have had your populist-right Trump types form their own group although now it makes more sense to think of your TRUE CONSERVATIVE!! types splitting off with the Republicans becoming this odd vaguely populist-right party.  The Libertarians probably would get in to Congress from the current minor parties (as might the Greens but whatever the new Social Democratic party is might take their support from them): you'd probably get someone trying to form a vague party of the centre supporting the status quo (liberal economics: not rocking the boat on social issues either way) but those sort of parties have fallen back globally in recent years.  You'd still basically have a two bloc system; its just that the factions within those blocs are separate parties rather than loose factions.

This is not meant to be realistic, it's just meant to be a fantasy party system.