Democrats in the House of Representatives on Wednesday launched a long-shot legislative maneuver to force a vote on immigration reform this year.

The effort is almost certain to fail, a reality that even top House Democrat Nancy Pelosi has admitted.

Democrats would need a majority of House members (218) to sign a discharge petition to force a vote on their comprehensive immigration bill. Even if all Democrats signed the petition, which may not happen, they would still need 19 Republicans to join them. And so far, none have said they will break with their party and sign it.

But the discharge petition serves a greater purpose: it helps Democrats — and activists aligned with their cause — hammer Republicans on immigration policy.

Midterm elections are coming up in November. And while Republicans don’t stand to lose many seats by ignoring immigration reform, there are certain races where it could make a difference. The discharge petition gives immigration reform hopefuls a concrete, if unobtainable, purpose.

Here are the Republicans who will take heat over immigration in the coming months:

The friendlies

Hardly any Republicans have been willing to cosponsor the House Democrats’ immigration reform bill. But the three Republicans who did sign onto the legislation aren’t getting much back for their commitment.

Reps. Jeff Denham (Calif.), David Valadao (Calif.) and Ileana Ros-Lehtinen (Fla.) all agreed to cosponsor the immigration reform bill in the House. Now, they’ll face pressure from activists who say they should sign the discharge petition.

So far, they’re not blinking. All three said they would not sign the petition.

“The fact of the matter is a discharge petition is not legislatively productive, it’s a political maneuver,” said Anna Vetter, a spokesperson for Valadao. “I think it muddies the water too much. It makes some people back off who were open to a conversation.”

The demographically vulnerable

Immigration might not be the number one concern for Latinos and Asians (that’s the economy and jobs), but remains an important issue in many of those communities.

Activists will keep the pressure on the Republicans who represent districts with a concentration of voters who might care about immigration reform, according to Dawn Le, the deputy campaign manager for the Alliance for Citizenship, a pro-reform coalition that includes labor unions and liberal activist organizations.

“Their constituents care about this issue, so it’s an opportunity to show whether they represent their constituents,” she said.

On that list: Reps. Mike Coffman (Colo.), Joe Heck (Nev.), Michael Grimm (N.Y.), Peter King (N.Y.) and Dave Reichert (Wash.).

The House Democrats’ campaign arm issued a press release on Wednesday afternoon highlighting Coffman’s lack of support for their immigration bill, saying he “refused yet again to take action” on immigration reform. Similar messages were sent about other Republican candidates, the release said.

Rep. Cory Gardner, who is running for Senate in Colorado, is also likely to be targeted.

These members “can either step up and help fix it or be held responsible for the failure,” Le said.

The takeaway: Republicans may ignore immigration reform this year, but supporters of a policy change can use tactics like this to keep the pressure on certain elected officials.

Ted Hesson was formerly the immigration editor at Fusion, covering the issue from Washington, D.C. He also writes about drug laws and (occasionally) baseball. On the side: guitars, urban biking, and fiction.