Sen. John McCain John Sidney McCainKelly's lead widens to 10 points in Arizona Senate race: poll COVID response shows a way forward on private gun sale checks Trump pulls into must-win Arizona trailing in polls MORE (R-Ariz.) is on a collision course with House conservatives over immigration reform.

Throughout his Senate career, McCain has clashed with House Republican lawmakers over high-profile issues, including campaign finance reform, detainee interrogation techniques, earmarks and tax cuts. This year, McCain has ripped Republicans in the lower chamber for not agreeing to enter into a budget conference with the Senate.

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Some political observers believe it’s just a matter of time before McCain aggressively goes after House GOP members for not voting on the Senate-passed immigration measure.

The five-term senator has stopped short of criticizing Speaker John Boehner John Andrew BoehnerLongtime House parliamentarian to step down Five things we learned from this year's primaries Bad blood between Pelosi, Meadows complicates coronavirus talks MORE’s (R-Ohio) vow to move immigration reform only if a majority of House GOP lawmakers are on board. Yet, McCain made a pointed comment last weekend that suggested he would only bite his tongue for so long.

“I really don’t feel it's appropriate for me to tell [Boehner John Andrew BoehnerLongtime House parliamentarian to step down Five things we learned from this year's primaries Bad blood between Pelosi, Meadows complicates coronavirus talks MORE] exactly how he should handle this. But I think Republicans realize the implications for the future of the Republican Party in America if we don't get this issue behind us,” McCain said on “Fox News Sunday.”

Rep. Steve King (R-Iowa), who strongly opposes the Senate bill, took issue with McCain’s warning, but said he expects the 2008 GOP presidential nominee to continue challenging conservatives on the airwaves.

“Most of what [McCain] will do, in my anticipation is through the media. … He likes to drop a little bomb and watch how people will react, and he’ll do it again,” King said in an interview with The Hill.

King said McCain “should have learned his lesson” when he tried to pass immigration reform with the late Sen. Edward Kennedy (D-Mass.).

McCain's office did not respond to comment for this article.

Sen. Charles Schumer Chuck SchumerDemocrats scramble on COVID-19 relief amid division, Trump surprise Pelosi, Schumer 'encouraged' by Trump call for bigger coronavirus relief package Schumer, Sanders call for Senate panel to address election security MORE (D-N.Y.) teamed up with McCain and six other senators to craft the immigration bill, which includes a pathway to citizenship.

Schumer has predicted that by the end of this year, the House will vote on the Senate-passed immigration measure. McCain and Schumer have forged a close relationship over the last six months.

Jim Manley, a former senior staffer for Senate Majority Leader Harry Reid Harry Mason ReidSenate Republicans signal openness to working with Biden Mellman: The likely voter sham Bottom line MORE (D-Nev.), pointed out the stark differences between the GOP-led House and Democratic-controlled Senate.

“The idea of compromise that Sen. McCain and others are pushing is at odds with a great majority of where the House Republican caucus is right now. [House Republicans] see compromise as a dirty word and they sure as heck don’t trust the Senate,” the Quinn & Gillespie Associates Public Affairs senior director said.

Manley added that if McCain “were to ratchet up the pressure, I think it would be counterproductive.”

A few House Republicans, including Reps. Ted Poe Lloyd (Ted) Theodore PoeSheila Jackson Lee tops colleagues in House floor speaking days over past decade Senate Dem to reintroduce bill with new name after 'My Little Pony' confusion Texas New Members 2019 MORE (Texas), Randy Forbes James (Randy) Randy ForbesBottom line Selection of Sarah Makin-Acciani shows the commitment to religious liberty Too much ‘can do,’ not enough candor MORE (Va.) and Walter Jones (N.C.), didn’t endorse McCain in the 2008 general election.

House Republicans are pressing for stronger border security provisions, but proponents of the Senate measure, including McCain, have strongly defended the upper chamber’s provisions on the issue.

McCain helped lead the effort to kill Senate Minority Whip John Cornyn John CornynSenate Republicans signal openness to working with Biden Hillicon Valley: DOJ indicts Chinese, Malaysian hackers accused of targeting over 100 organizations | GOP senators raise concerns over Oracle-TikTok deal | QAnon awareness jumps in new poll Republican Senators raise concerns over Oracle-TikTok deal MORE’s (R-Texas) border-security amendment. McCain called the amendment “a poison pill.”

The 76-year-old senator has not been shy in criticizing members of his party.

In 2004, McCain engaged in a high profile back and forth with then-Speaker Dennis Hastert (R-Ill.) over tax cuts.

At the time, the U.S. was engaged in battles on two fronts: Afghanistan and Iraq. McCain blasted the House GOP for seeking to cut taxes when the deficit was ballooning.

McCain charged, “As mind-boggling as expanding Medicare [to include a prescription drug benefit] has been, nothing tops my confusion for cutting taxes during wartime. I don’t remember ever in the history of warfare when we cut taxes.”

Asked about McCain's attack, Hastert responded at the time, “Who? Where's he from? A Republican?”

A source who has worked with McCain said, “It’s easy to assume that because he enjoys the spotlight, that he requires it, but that's not necessarily the case. [McCain] is smart enough to realize that it’s to the benefit of the legislation for other people to take the lead. He’s more than willing to let that happen.”

The source, who requested anonymity, stressed that he has no direct knowledge of McCain’s current thinking.

Former Hastert communications director John Feehery said McCain knows how to legislate.

“McCain knows the legislative process, and he knows that the game is trying to get to [a House-Senate] conference, and the House has to find its own way to get to conference,” said Feehery, a columnist for The Hill.

“I think the best messenger to House conservatives is [Sen.] Marco Rubio Marco Antonio RubioHillicon Valley: DOJ indicts Chinese, Malaysian hackers accused of targeting over 100 organizations | GOP senators raise concerns over Oracle-TikTok deal | QAnon awareness jumps in new poll Intelligence chief says Congress will get some in-person election security briefings Republican Senators raise concerns over Oracle-TikTok deal MORE [R-Fla.], not John McCain,” said Feehery, who added that former Rep. and now-Sen. Jeff Flake Jeffrey (Jeff) Lane FlakeRepublican former Michigan governor says he's voting for Biden Maybe they just don't like cowboys: The president is successful, some just don't like his style Bush endorsing Biden? Don't hold your breath MORE (R-Ariz.) could also play a pivotal role.