Montana's Democratic Senator Jon Tester accused of 'covering up' Biden's decline in brutal ad launched in battleground state

Democratic Sen. Jon Tester lied about Joe Biden's ability to do the job of president—that is the brutal message of a new attack ad in Montana, a high stakes election contest where both sides know that victory in November could deliver control of the Senate.

The 30-second spot, produced by More Jobs, Less Government, a super PAC supporting his Republican opponent Tim Sheehy, goes up on Tuesday.

It opens with Democrat Tester's own words. 

'Joe Biden, when I've been around him, and that's not every day ... he's absolutely 100 per cent with it,' he says in the ad produced by More Jobs, Less Government, a super PAC supporting his Republican opponent Tim Sheehy.

'That wasn't true, says the narrator. 'Tester lied.' 

A new ad from supporters of Republican candidate Tim Sheehy highlights Sen. Jon Tester's previous claims that Joe Biden was up to the job of president

The angle has become a common line of attack for Democrats after Biden bowed to weeks of pressure and ended his run for reelection last month. 

Republicans and their supporters have an arsenal drawn from months of quotes from Democratic lawmakers playing down health concerns and insisting that Biden was as fit as someone decades younger.

Their claims ring hollow after Biden fell apart during his first televised debate with Donald Trump in July. 

The ad will run for the remainder of the month in the three key TV markets of Helena, Missoula and Great Falls, as well as online, as part of a seven-figure buy.. 

'Jon Tester sold Montanans out by knowingly lying about Joe Biden's mental decline for years,' said Andy Surabian, chief strategist to More Jobs, Less Government. 

'While he might be running away from Biden today, he was one of his biggest boosters and defenders from the moment he was elected.

'Tester voted for the Biden-Kamala agenda 95% of the time and would be a vote for liberal Chuck Schumer as Senate Majority Leader.'

Tester initially stood by Biden after his disastrous debate performance, but eventually said he should drop out on July 18, three days before the president announced he would stand aside.

Less than a year earlier he was rubbishing reports that Biden was not the man he once was. 

Tim Sheehy, a former Navy SEAL, is the Republican candidate. He has the backing of Donald Trump who is due to campaign with him in Bozeman on Friday evening

The 30-second ad goes up on Tuesday and runs for the rest of the month in a battleground state that both sides believe could be crucial to controlling the Senate

Tester has held the seat since 2007 but Trump won the state easily in 2016 and 2020

'Biden's fine. He's doing a great job,' he told NBC News, last August, in a clip included in the ad. 

The ad also accuses him of backing the Biden-Harris administration at every turn. 

Tester has held the Montana seat since 2007, in a state that heavily backed Trump during the 2020 election.

Republicans see the battle as crucial to their hopes of taking control of the Senate. 

They expect to pick up a seat in West Virginia, where Democrat-turned-independent Joe Manchin is retiring, and need just one more to secure a majority in the upper chamber.

The result is that millions of dollars is pouring into the battle between Tester and Sheehy, a former Navy SEAL. 

Latest campaign finance report show Tester has raised more than $43.7, a record amount, and three times more than he had collected by this stage in his 2018 race.

Sheehy has raised $13.7 million since entering the contest a year ago.

The importance of the race will be on full display on Friday, when former President Donald Trump holds a rally in support of Sheehy.

He won the state by more than 16 points in 2020 and by more than 20 points over Hillary Clinton in 2016.