Another Republican senator to resign, setting up November election that could further expose party divisions

Democrats only need a net gain of two seats to win a majority in the Senate

Republican Senator Thad Cochran of Mississippi has announced that he will resign from the US Senate (Getty Images )

Republican Senator Thad Cochran has announced he will resign on April 1, setting up another election in November that could further expose divisions in the Republican Party.

Mr Cochran’s resignation only complicates matters for Republicans in what’s expected to be a dramatic and vicious battle for control of the US Senate and House of Representatives this year.

The 80-year-old is one of the longest-serving senators in US history. He has been dealing with health problems in recent months and was absent for several weeks in the Senate last fall as he recuperated from a urinary tract infection.

“I regret my health has become an ongoing challenge,” Mr Cochran said in a statement. “I intend to fulfill my responsibilities and commitments to the people of Mississippi and the Senate through the completion of the 2018 appropriations cycle, after which I will formally retire from the US Senate.” He is currently chairman of the Appropriations Committee, a powerful panel with jurisdiction over government spending.

In November, Democrats only need a net gain of two seats to win a majority in the 100-member upper chamber. Meanwhile, the party needs a net gain of 24 to retake control of the 435-member House.

Significant losses of seats could further impede President Donald Trump’s agenda, which has already struggled under the slim Republican majority in the Senate.

Mississippi will now have two Senate seats up for grabs, with the special election for Mr Cochran’s seat being held on the same day as the regularly scheduled midterms.

But the tough races may come well before November. Hard-right conservative Chris McDaniel, who lost to Mr Cochran in a nasty 2014 primary, announced last week that he would run against incumbent Republican Senator Roger Wicker.

On Monday, Mr MrDaniel did not rule out switching to running for Mr Cochran’s seat.

“I am currently focused on my campaign against Roger Wicker, but all options remain on the table as we determine the best way to ensure that Mississippi elects conservatives to the United States Senate,” Mr McDaniel said.

The conservative firebrand represents possibly one of the last chances for ex-White House Chief Strategist Steve Bannon to see the fruit of his efforts to wage war against the Republican establishment.

So far, Mr Bannon has been unsuccessful. In last year’s Alabama Senate special election, Mr Bannon backed Roy Moore, whose campaign was upended after the evangelical voter favourite was accused of sexual misconduct. Mr Moore vehemently denied the allegations.

The conservative state ultimately ended up electing Democrat Doug Jones to the Senate, making him Alabama’s first Democratic US senator in more than 25 years.