Sen. Bob Menendez is promising he will be cleared of charges of bribery and corruption at his trial that starts Wednesday, but Republicans in Washington are launching an aggressive campaign now to get his colleagues to pressure him to resign if convicted.

The effort by the Republican National Committee will be aimed at the New Jersey senator's fellow Democrats, including Minority Leader Chuck Schumer of New York; senators running for re-election in states that President Trump won last year; and those with potential aspirations for the presidency in 2020, such as Sens. Cory Booker of New Jersey and Elizabeth Warren of Massachusetts.

Booker called the GOP campaign "offensive."

Republicans want to make sure Menendez would not remain in office while awaiting sentencing or appealing his conviction because New Jersey's Republican governor, Chris Christie, would get to name an acting senator if there is a vacancy before Christie's term ends in mid-January.

That would give the GOP a 53rd seat in the Senate at least until the midterm elections are held in 2018. New Jersey has not elected a Republican to the Senate since 1972, and the Democrat vying to succeed Christie, Phil Murphy, had a lead of 27 percentage points in a July poll over Lt. Gov. Kim Guadagno, the Republican nominee.

If Menendez is convicted and refuses to leave office, the Constitution gives the Senate the power to remove him with a two-thirds vote — a 67-vote tally that would require 15 Democrats to join all 52 Republicans. The last New Jersey senator convicted of corruption in office, Harrison Williams, was convicted in May 1981 but did not resign until March 1982, as the Senate was preparing to expel him.

The GOP pressure campaign includes ads on social media that highlight how Democrats, including then-senator Barack Obama of Illinois, said in 2008 that Sen. Ted Stevens, R-Alaska, needed to resign after he was convicted of corruption.

Stevens was just the fifth senator in history convicted while in office. The conviction came in October 2008 during a re-election campaign in which Stevens was defeated, but he continued to serve until his term ended the following January. Stevens' conviction was overturned prior to sentencing after a Justice Department investigation found prosecutorial misconduct.

For Menendez, Republicans are setting up a war room to track coverage of the trial and disseminate any potentially embarrassing details that emerge. The party will also have "trackers" try to get senators in their home states say whether they want Menendez to stay.

"Convicted felons can't even vote in many parts of the country, but Democrats are going to let one keep voting in the United States Senate?" said Michael Ahrens, an RNC spokesman. "If Democrats don't call for a convicted felon to resign immediately and instead force taxpayers to keep paying his salary, that's a debate we're ready to have."

Circling:Stile: As Menendez' trial looms, both parties plot for his seat

Story so far:Bob Menendez trial: Timeline of events leading up to the corruption trial

The facts:The trial of Sen. Bob Menendez: What you need to know

Booker said his office and Menendez's staff are working closely on Senate business this month, including efforts to secure funding for a new rail tunnel under the Hudson River. He said he had not heard of an effort to get Democrats to turn on Menendez.

"I find that a bit offensive," Booker said. "We still hold true to the principle in this country that you’re innocent until proven guilty and to even engage in that kind of hypothetical, I think, is unfair and wrong... I’m not going to entertain what’s happening after this trial."

Menendez, 63, was accused in a 2015 indictment of using his office to benefit the personal and business interests of co-defendant and longtime friend Salomon Melgen, 63, of North Palm Beach, Fla. Melgen, a wealthy ophthalmologist, allegedly paid bribes in the form of luxury travel, including flights on his private plane to his villa in a Dominican resort, and more than $700,000 in contributions to super PACs and political committees that helped Menendez get re-elected in 2012.

In a radio interview in Michigan on Wednesday, RNC Chairman Ronna McDaniel said the trial deserves more public attention because of the charges involved.

"It is astounding to look at the counts against him and the bribery counts against him," she said. "He took 19 free rides with this gentleman, he helped get visas for his girlfriend, this big donor."

Menendez and Melgen have pleaded not guilty and tried with virtually no success for more than two years to have courts, up to the U.S. Supreme Court, throw out the indictment. The trial is expected to last two months, and if Menendez is convicted, he will likely appeal. Legal experts say he may benefit from a 2016 Supreme Court ruling that overturned the conviction of the former governor of Virginia by narrowing the definition of bribery, as well as an earlier court ruling that said contributions to super PACs are not corrupting to officials because the money is spent independently of their campaigns.

“Senator Menendez has said he’s going to continue working on behalf of the people of New Jersey who entrusted him with this office until he no longer decides to do so,” said Menendez spokesman Michael Soliman. “He’s going to vote when his vote is needed, he’s going to continue to travel the state with his colleague, Senator Booker, fighting on behalf of all New Jerseyans.”

Menendez is preparing to run for re-election in 2018, and he had $3.7 million in his campaign account on June 30. No Republican has yet announced plans to challenge him.

The national Republican effort is partnering with New Jersey's GOP to try to put pressure on Murphy as he seeks to replace Christie, as well as Booker and Menendez.

As of last week, however, Christie himself had not jumped on board, saying that Menendez "deserves a presumption of innocence."

"We'll see what happens in this trial. We don't know if there's even going to be a vacancy," Christie said last week on MSNBC. "Bob Menendez, we've had plenty of political differences and policy differences with over the years. He deserves the presumption of innocence."