WASHINGTON — Republicans and Democrats will put good will to the test when Congress returns this week to potentially incendiary fights over nominations, unresolved disputes over student loans and the farm bill, and uncertainty of whether lawmakers have the political will to rewrite immigration laws.
The cooperation evident in the Senate last month with passage of a bipartisan immigration bill could be wiped out immediately if majority leader Harry Reid, Democrat of Nevada, frustrated with GOP delaying tactics on judges and nominations, tries to change the Senate rules by scrapping the current three-fifths majority for a simple majority.
Republican leader Mitch McConnell of Kentucky has indicated it’s a decision Reid could regret if the GOP seizes the Senate next year.
‘‘Once the Senate definitively breaks the rules to change the rules, the pressure to respond in kind will be irresistible to future majorities,’’ McConnell said last month, looking ahead to 2014 when Democrats have to defend 21 seats to the GOP’s 14.
McConnell envisioned a long list of reversals from the Democratic agenda, from repealing President Obama’s health care law to shipping radioactive nuclear waste to Yucca Mountain in Reid’s home state of Nevada.
Recently elected Democrats have clamored for changes in Senate rules as Obama has faced Republican resistance to his nominations.
Two Cabinet-rank choices — Tom Perez as labor secretary and Gina McCarthy to head the Environmental Protection Agency — could be approved by the Senate this month after a loud debate over administration policies.
The GOP also has challenged Obama’s three judicial nominees to the US Court of Appeals for the District of Columbia Circuit as they have tried to eliminate vacancies.
Reid served notice in April that the Democratic majority could change the Senate rules on ‘‘any given day,’’ and he was willing to do so if necessary.
In the Republican-controlled House, courteous behavior, even within the GOP ranks, has barely been perceptible with the ignominious failure of the farm bill. Some collaboration will be necessary if the House is to move ahead on immigration legislation this month.
Conservatives from safe, gerrymandered House districts have rebuffed appeals from some national Republicans who argue that embracing immigration overhaul will boost the party’s political standing with an increasingly diverse electorate, especially in the 2016 presidential election.Conservatives strongly oppose any legislation offering legalization to immigrants living here illegally.
Reflecting the will of the rank and file, House Speaker John Boehner of Ohio and other Republicans have said the comprehensive Senate immigration bill that couples the promise of citizenship for those living here unlawfully with increased border security is a nonstarter in the House.
Republicans were assessing the views of their constituents during the weeklong July Fourth break and planned to discuss their next steps at a private meeting Wednesday.
‘‘I think what members need before we proceed on the actual immigration reform is an ironclad guarantee that the border is going to be secure,’’ Representative Matt Salmon, an Arizona Republican, said just before the recess. Salmon didn’t see any urgency to acting quickly.
‘‘I find it very interesting the argument that we can’t wait till the border is secure, we can’t even do a six-month test to make sure,’’ he said.
Representative Michael McCaul of Texas, who chairs the House Homeland Security Committee, said Republicans would be hashing out ‘‘two key hot spots’’ in Wednesday’s meeting: the pathway to citizenship and health care.
The House Judiciary Committee has adopted a piecemeal approach, approving a series of bills, none with a path to citizenship that Obama and Democrats are seeking. Democrats hope the single-issue bills get them to a conference with the Senate, where the prospects for a far-reaching overhaul improve.
A more pressing concern for some lawmakers was the fate of the five-year, half-trillion-dollar farm bill. In a surprise last month, the House rejected the bill as 62 Republicans voted no after Boehner had urged support.
House conservatives wanted cuts deeper than $2 billion annually, or about 3 percent, in the almost $80 billion-a-year food stamp program, while Democrats were furious with a last-minute amendment that would have added additional work requirements to food stamps.
Reid has made it clear that an extension of the current farm law, passed in 2008, is unlikely as he presses the House to pass the Senate version of the bill. That leaves Boehner to figure out the next step before the current policy expires Sept. 30.
Congress also must figure out what to do about interest rates on college student loans, which doubled from 3.4 percent on July 1 because of partisan wrangling in the Senate.