For the past few months, there hasn't been any urgency in Congress to legalize the undocumented immigrants who were brought into the country as children. Court cases forced the program known as Deferred Action for Childhood Arrivals to stay open beyond when President Trump planned to shut it down in March.

But some Republicans in Congress are suddenly feeling the creep of a new deadline: the election.

More than a dozen House Republicans are issuing a rare challenge to their own party's leaders: Allow immigration bills to get a vote now, or we'll force a vote.

They're circulating a petition to do just that, and it's only seven signatories shy of overriding House Speaker Paul D. Ryan's (R-Wis.) opposition and forcing votes on a variety of immigration bills to provide a path to citizenship for “dreamers.” It would be the first time the House has passed an immigration bill since Republicans came to power in 2011.

The fact that Republicans are challenging their own leaders to get something done on immigration is remarkable, but their challenge is still a long shot. “The chance that it will work is so small that this is really a Hail Mary,” said Alex Nowrasteh, an immigration policy analyst with the libertarian Cato Institute.

Here's why:

1. Those last seven GOP lawmakers will be much harder to get than the first 18: So far 18 Republicans have signed onto the discharge petition (that's the petition's parliamentary name). Once 25 Republicans sign on, all 193 Democrats are expected to, as well, and that would be enough to force a vote over leadership's objections.

But the first 18 GOP lawmakers was the easy part; many of the Republicans who immediately signed onto this petition found it a political no-brainer. They represent swing districts or districts with a high population of dreamers. At least four signatories are retiring.

The rest of Republican lawmakers face a much more difficult decision on whether to buck leadership, said Molly Reynolds, a congressional expert with Brookings Institution, in an email: “Majority party legislators are often afraid of the consequences of undermining the power of their party leaders to make decisions about what gets considered on the floor.”

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2. Some Republicans see this as biting the hand that feeds them: Rep. Don Bacon (R-Neb.) is facing a competitive reelection in a year where Democrats are performing exceptionally well. He'd really like his party's help in November to keep his job.

Lawmakers like Bacon have calculated that that means keeping Ryan happy. Even though Ryan is retiring, he's still a prolific fundraiser; just last week Politico reported he played a role in getting GOP mega-donor Sheldon Adelson to sign a massive $30 million check to a House Republican super PAC.

“I feel like it puts our leadership in a bad spot,” Bacon told The Post's Mike DeBonis on Thursday when explaining why he's not ready to sign the petition.

Facing pressure from the petition and likely with lawmakers like Bacon in mind, Ryan said last week he would “like to” put an immigration bill for a vote before the election. But that may not solve the underlying problem: It's not clear whether the bill he would put forth would satisfy Republicans and Democrats who want to protect dreamers.

3. Trump: Just because the House passes something on immigration doesn't mean it will become law. After four versions of bills to protect dreamers failed in the Senate in February, Senate Majority Leader Mitch McConnell (R-Ky.) said he was done with immigration for the year. And then there's Trump, who — Ryan has pointed out — has threatened to veto a path to legalization for dreamers that doesn't include his more hard-line demands on cuts to the legal immigration system.

Trump has been very inconsistent on what he wants on immigration. But lately he has decided that the No. 1 item on his immigration wish list is to end the diversity visa lottery program and curb programs allowing U.S. citizens to sponsor family members' visas. “It seems like he's willing to not have his wall if it means he can't get cuts in legal immigration,” Nowrasteh said.

All those things are nonstarters with most Democrats and some Republicans. That means any bill that carries Trump's proposals almost certainly wouldn't pass the House, and it almost certainly wouldn't satisfy signatories of this petition.

4. Discharge petitions rarely succeed: “Most discharge efforts fail,” writes George Washington University political science professor and Brookings analyst Sarah Binder in The Post's Monkey Cage blog.

She calculated that in the past 80 years, more than 97 percent of discharge petitions have fallen flat. That's because discharge petitions violate the rule that defines the House more than any other: The majority party decides what gets voted on.

The majority party seems reluctant to allow a vote on the kinds of dreamer bills that could most likely pass the House. More important, so far all but 18 House Republicans are just as reluctant.