A relatively obscure federal agency is increasingly becoming the scene of a proxy battle within the Republican party over the free market.

The Export-Import bank, which guarantees loans for U.S. businesses that want to do risky-ish business abroad, is currently closed after Congress let its June 30 reauthorization date pass without doing anything. The bank's temporary closure is a win for tea-party conservatives, who are now fighting to keep it shuttered. It's the first step to ending "crony capitalism," they say.

The bank's supporters argue that the independent agency is necessary for U.S. business to compete abroad. Supporters won a vote in the Senate on Sunday to reopen the self-sustaining bank. But its fate in the House of Representatives is uncertain -- the bank's reauthorization isn't even set for a vote in the House.

[Republicans turn on one another in Export-Import Bank battle]

Sunday's vote split the Republican party almost right down the middle. As the bank becomes the latest litmus test for conservatives, it's splintering the party even further.

Given the level of nuance in this debate, we thought we would break it down for you. Here are four factions Republicans fall into on the Export-Import Bank:

1. Longtime anti-Ex-Im crusaders

Rep. Jeb Hensarling (R-Tex.), an outspoken bank opponent. (Drew Angerer/Bloomberg)

When the bank was last reauthorized in 2012, it was not nearly as controversial. Back then, a solid majority of House Republicans supported keeping the 81-year-old institution going, joining all House Democrats in a yes vote of 330 to 93.

Among those 93 House Republicans who opposed the bank was a growing group of hard-core opponents who viewed its demise as one of the first steps toward ending the federal government's involvement in the private sector.

[The Export-Import Bank explained for those who don't know what that is]

They included fiscal conservative leaders such as Rep. Jeb Hensarling (R-Tex.), who chairs the powerful House Financial Services Committee, and Rep. Bill Flores (R-Tex.), who chairs the large conservative coalition the Republican Study Committee.

Key talking point: “If you’re going to start cutting the weeds out of the federal government, this is one of the first weeds you need to root out," Flores said.

2. Bandwagon anti-Ex-Im crusaders

Former Florida governor Jeb Bush announces his 2016 presidential bid in Miami last month. (Charles Ommanney/The Washington Post)

This time around, Republican opponents of the bank have a lot more friends — as in, nearly every GOP 2016 presidential candidate.

These new opponents join with what The Washington Post's Matea Gold and Tom Hamburger describe as a fierce lobbying campaign by tea party-aligned groups such as Heritage Action and the Club for Growth and mega-GOP donors Charles and David Koch to get rid of the bank.

[Inside the GOP fight over the influential Export-Import Bank]

All that lobbying seems to have moved the Republican party to the right by making the bank a litmus test for conservative support in 2016. For example, former Florida governor Jeb Bush was affiliated with a Florida company that received $74 million in loan guarantees from the bank to sell a water pump in Nigeria. Now, he's against it.

This camp includes three of the four senators running for president, as well as most governors in the race: Bush, Wisconsin's Scott Walker, Louisiana's Bobby Jindal and former Texas governor Rick Perry.

Key talking point: "I am willing to use any and all procedural tools to stop this corporate welfare, this corruption, from being propagated," said Sen. Ted Cruz (R-Tex.), a 2016 candidate and one of the bank's highest-profile opponents this time around. 

3. Opponents who don't much care either way

Senate Majority Leader Mitch McConnell (R-Ky.) (AP Photo/Evan Vucci)

There are high-profile Senate Republicans who didn't support the bank in 2012 and don't support it today, but unlike crusaders, have not made getting rid of it one of their top priorities.

This group includes Republican leaders such as Senate Majority Whip John Cornyn (Tex.) and Senate Majority Leader Mitch McConnell (Ky.). They were among 19 senators who voted against the bank back then, a number that has grown to 26 this time around. This group of opponents doesn't agree with the bank's role in the private sector — they point to the fact that 87 percent of the bank's loans go to major corporations such as Boeing, General Electric and Caterpillar — but they aren't willing to make shutting it down a crusade.

Key talking point: "Just let it go," said Rep. Paul Ryan (R-Wis.), the party's 2012 vice presidential nominee.

4. Business Republicans who support the bank

Sen. Lindsey Graham (S.C.), the lone GOP 2016 presidential candidate to support the bank. (Brendan McDermid/Reuters)

Most Republicans used to fall into this category, but their numbers are dwindling as the bank's opponents grow in prominence.

This group includes pro-business Republicans and Republican-leaning groups like the Chamber of Commerce. One of the lone 2016 candidates to support the bank  is Sen. Lindsey Graham (S.C.), who represents a state in which Boeing, a major recipient of bank loans, is a big employer.

And even though business Republicans won Sunday night's vote to reopen the bank with a filibuster-proof majority, they are arguably the biggest losers in this debate. Not long ago, this group dominated the Republican Party. Now, they're fighting to be heard among a growing number of tea-party and increasingly conservative Republicans.

Key talking point: "Ex-Im is one of the most important tools at the disposal of U.S. companies to level the playing field for trade finance as they seek to increase exports and create jobs at home," the Chamber of Commerce said in a recent statement.