Senate Republicans were expecting to cast a key procedural vote early Wednesday afternoon to begin debate on tax reform, but the timing has slipped some as lawmakers scramble to make last-minute adjustments.

Senate Republican Whip John Cornyn John CornynTumultuous court battle upends fight for Senate Texas Democrats roll out first wave of planned digital ads as Election Day nears Calls grow for Biden to expand election map in final sprint MORE (R-Texas) said the bill is being held up because of “technical issues” but said GOP leaders have enough votes to advance the tax bill.

“There’s some technical issues that may delay the vote a little bit,” he said.

GOP aides earlier on Wednesday said they expected a vote to proceed to the tax bill to take place about 2 p.m., but there are still some loose ends to wrap up.

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Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellGraham: GOP will confirm Trump's Supreme Court nominee before the election Trump puts Supreme Court fight at center of Ohio rally The Memo: Dems face balancing act on SCOTUS fight MORE (R-Ky.) would only tell GOP colleagues at lunch that a vote will take place sometime Wednesday afternoon.

Several Republicans with concerns over the bill shuttled in and out of McConnell’s office: Sens. Steve Daines Steven (Steve) David DainesMcConnell locks down key GOP votes in Supreme Court fight Will Republicans' rank hypocrisy hinder their rush to replace Ginsburg? Toobin: McConnell engaging in 'greatest act of hypocrisy in American political history' with Ginsburg replacement vote MORE (Mont.), John McCain John Sidney McCainBiden's six best bets in 2016 Trump states Replacing Justice Ginsburg could depend on Arizona's next senator The Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy MORE (Ariz.), Bob Corker Robert (Bob) Phillips CorkerHas Congress captured Russia policy? Tennessee primary battle turns nasty for Republicans Cheney clashes with Trump MORE (Tenn.) and Susan Collins Susan Margaret CollinsGraham: GOP will confirm Trump's Supreme Court nominee before the election Gardner signals support for taking up Supreme Court nominee this year Tumultuous court battle upends fight for Senate MORE (Maine).

Sen. Tom Tillis (R-N.C.), who presided over the Senate floor during lunch, said he expected a vote on the tax bill in the 4 p.m. to 5 p.m. timeframe.

Senate Republican Conference Chairman John Thune John Randolph ThuneGraham: GOP will confirm Trump's Supreme Court nominee before the election Tumultuous court battle upends fight for Senate What Senate Republicans have said about election-year Supreme Court vacancies MORE (S.D.) said leaders are in talks with the Senate parliamentarian over whether a proposal to limit tax relief in case of underwhelming economic growth meets the procedural requirements of the budget process.

The so-called “trigger” is an important concession to Republicans concerned about the deficit, such as Corker and Sen. James Lankford James Paul LankfordMcConnell works to lock down GOP votes for coronavirus bill Charities scramble to plug revenue holes during pandemic Warren calls for Postal Service board members to fire DeJoy or resign MORE (R-Okla.).

The details of the compromise have not yet been made public and conservative groups are pushing back hard against the idea.

Club for Growth President David McIntosh said, “The idea of a ‘tax hike trigger’ should be rejected on its merits.”

“It will have harmful impacts on American businesses and undermine any economic growth potential in this tax reform bill because businesses will not invest due to the possibility of a higher tax rate,” he said.

Grover Norquist, president of Americans for Tax Reform, warned that a trigger would create uncertainty in the private sector.

“The key to pro-growth tax reform is permanence and certainty,” he said. “No one invests in response to ‘maybe.’ A trigger that threatens tax hikes is a self-fulfilling threat to kill jobs.”

- This report was updated at 2:40 p.m. EST