On Capitol Hill, Donald Trump's group of friends is growing by the day. That's partly out of necessity: He's the Republicans' presumptive presidential nominee, and most congressional Republicans supporting him seem to be doing so because, well, they feel he'd better than Hillary Clinton. (We're looking at you, Paul Ryan!)

But a handful of Republicans aren't just going through the motions with Trump. They're actively, unequivocally and enthusiastically trying to get him to the White House. Some endorsed Trump way back in February when it wasn't even clear who would emerge as Republicans' nominee.

"My colleagues looked at me as kind of a man on an island," said Rep. Chris Collins (R-N.Y.). He and Rep. Duncan Hunter (R-Calif.) were the first sitting member of Congress to endorse Trump.

Now, Trump's early endorsers are playing a pivotal role in helping the nominee expand his appeal in Washington. They even hold weekly strategy meetings with Trump's campaign (that have become standing-room only) to talk policy and politics.

Here's a list of Trump's top six allies in Congress. They are loosely ranked in order, with 1-3 being the most ardent Trump supporters. To the line!

6. Rep. Tom Price: Trump's Hill allies say Price, the Georgia Republican and chairman of the powerful House Budget Committee, has been instrumental in getting other committee chairs on board. At least nine House chairmen have endorsed Trump so far.

5. Reps. Tom Marino and Lou Barletta: Okay, we cheated by putting two people in the fifth spot. But it's tough to mention one Pennsylvania Republican without the other. Trump insiders say both men's endorsements were crucial in helping Trump win Pennsylvania in April. That night, you'll recall, was Trump's five-state sweep in the Northeastern primary and seemingly the beginning of the end of the Republican nominating contests. Barletta is an immigration hard-liner who likes Trump's idea to build a wall, and Marino, who represents a conservative, more rural section of northeastern Pennsylvania, told Politico that endorsing Trump was "one of my life-changing moments."

4. Sen. Bob Corker: The Tennessee senator is consistently on folks' short list for Trump's veep pick. Corker chairs the powerful Senate Foreign Relations Committee and recently praised one of Trump's foreign policy speeches for "challenging the foreign policy establishment." Soon after that speech, Corker said he was willing to advise Trump on foreign policy. Sure enough, the two met in May in Trump Tower in New York to, in Corker's words, talk about "foreign policy and just the shape of the campaign." Corker has downplayed the veep speculation — he hasn't even officially endorsed the nominee, choosing instead to walk one of those support-but-not-endorse lines.

3. Sen. Jeff Sessions: The Alabama senator was the first sitting senator to endorse Trump, way back in February. And when he did, Sessions helped take Trump's presidential bid from possible to probable. Sessions is another hard-line immigration conservative whose support for Trump was a major blow to Sen. Ted Cruz, who was name-dropping Sessions every chance he got. Today Sessions helps shape Trump's national security platform. It seems the feeling is mutual: Trump told reporters Tuesday that Sessions is "certainly someone I would consider" for his No. 2, calling him a "fantastic person."

2. Rep. Duncan Hunter: The California Republican was one of the first sitting members of Congress to endorse Trump (he and Collins, below, essentially endorsed on the same day in February). Hunter has since been helping coordinate weekly meetings between Republican lawmakers and the Trump campaign at the Capitol Hill Club, and those meetings have become standing-room only. There are times when Hunter has been slightly critical of Trump — such as when he said Trump missed an opportunity to sway lawmakers the last time he was in town — but Hunter's staff maintains that's all part of being one of Trump's top liaisons and advisers on the Hill.

1. Rep. Chris Collins: Trump's other top Hill supporter is Collins, who has been national TV 75 to 80 times  as Trump's surrogate since endorsing him in February. Collins also helps organize those weekly meetings, and he considers himself the Hill's go-to guy to convince on-the-fence lawmakers to endorse Trump. "I've been sharing my thought process with fellow members," he said, "and in many cases got them agreeing my rationale [for endorsing Trump] makes sense."