Democratic nominee Hillary Clinton is outspending her rival Republican Donald Trump in television advertisement in the final week of campaign, from about 14 million dollars to 32 million dollars.

This came as both candidates hit battle grounds in a tightened race in Florida, North Carolina, Pennsylvania, Arizona and Nevada, according to data from Kantar Media/CMAG, a company that tracks political advertising.

Clinton’s 18 million-dollar last-minute spending included about five million dollars in additional airtime in Florida, a tight state that Donald Trump must win to reach the White House.

She is also putting money on the airwaves in Democrats stronghold states, seeking to deny Trump inroads into states seen as her wall of defense.

The Democratic candidate’s additional funds aimed to improve her reach in several key battlegrounds, such as Ohio, Pennsylvania and North Carolina.

Her campaign is also going up in Colorado, where it last advertised in late July, and Virginia, where it last ran advertisement in early August.

She is also running her first advertisement of the general election in Michigan and New Mexico.

Similarly, the Republican National Committee has made its first advertising buy in support of Trump, putting up 2.9 million dollars in five states.

The states are Florida, Michigan, Nevada, Colorado, New Mexico and Iowa, and a new advertisement referencing news of a Clinton-related probe by the Federal Bureau of Information (FBI).

Trump pledged to spend 25 million dollars on advertising this week, although he is about five million dollars short of that target.

The Republican nominee would need to increase his spending by about 15 million dollars to honor his pledge to spend 100 million dollars on television from late September to the date of the election.

Future45, a Republican super Political Action Committee, funded by the Adelson and Ricketts families, also plans to spend 10 million dollars on a television campaign in the closing days.

The candidates’ campaigns and outside groups supporting their bids will spend nearly 75 million dollars on television advertisements this week.

The Centre for Responsive Politics has reviewed its federal election spending estimate from last week’s 6.6 billion dollars to about seven billion dollars.

“We reran the numbers, and have a new-and-improved prediction for the total cost of the 2016 federal election.

“There is at least 6.9 billion dollars as the total cost of the 2016 federal election, about 350 million dollars more than we predicted last week,” the Centre said.

It said the biggest driver of the leap was spending by outside groups, which made up about 26 per cent of all total spending.

“These entities, mostly super-Political Action Committees that are not supposed to coordinate with campaigns, have spent almost 73 per cent more this year compared to 2012.”

Since 1998, the Republicans have usually outspent Democrats in the spending contest, with 2008 and 2004 being the only exceptions.

It is expected that the trend would continue this year with Republicans expected to spend about 216 million dollars more than Democrats, spending estimated 3.3 billion dollars compared to $3.1 billion.