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WASHINGTON (Reuters) - U.S. President Donald Trump plans to campaign aggressively on behalf of Republican candidates in the coming six weeks, holding as many as eight rallies and 16 fundraisers before the end of September.

Trump is likely to visit states that are crucial to Republican hopes for retaining control of the U.S. Senate, including Missouri, Montana, Nevada, North Dakota, and Tennessee, according to a person familiar with the president’s plans.

The president’s Republican party risks losing control of the House and Senate in the November election and thus losing the ability to advance much of the president’s political agenda. Though Trump’s overall popularity is low, he still retains strength among Republican voters.

Democrats need to gain two seats in November’s congressional elections to assume control of the Senate and 23 seats to take the House of Representatives.

The president will hold a rally on Tuesday evening in Charleston, West Virginia, on behalf of Senate candidate Patrick Morrisey, who is trying to unseat Democratic incumbent Senator Joe Manchin. He plans to visit Ohio on Friday in support of Senate candidate Jim Renacci, who is taking on Democratic incumbent Sherrod Brown.

As has been the case in campaign events over the summer, most of the states where Trump plans to campaign is friendly territory where he can energize the supporters who helped him win the 2016 presidential race. Trump’s political operation has estimated that one-third of those attending Trump’s rallies are not traditional Republicans.

Trump has tended to avoid areas where he is less popular. But the person familiar with the plans said that it remains possible Trump’s campaign schedule after September could include more hotly contested districts in suburban areas, home to moderate voters who have not warmed to the president.

Beyond rallies, Trump hopes to use his fundraising power to aid Republican candidates in tight races. He has raised $227 million on behalf of the Republican National Committee this cycle, as well as $75 million on behalf of candidates directly.