Republicans close in on Democrats in Michigan, North Carolina Senate races - Reuters/Ipsos poll

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By Jason Lange

WASHINGTON (Reuters) - Republican Senator Thom Tillis of North Carolina pulled even with his Democratic challenger, and in Michigan, the Republican candidate for a U.S. Senate seat cut into the Democratic incumbent's lead, Reuters/Ipsos polls showed on Tuesday.

There are about 12 competitive U.S. Senate races this year, 10 with vulnerable Republican incumbents and two with vulnerable Democrats. To have a majority in the Senate, Democrats need to pick up three seats if the party wins the White House, which gives the vice president a tie-breaking vote, and four if not.

Here are the latest results for three Senate races on which Reuters/Ipsos is polling:

NORTH CAROLINA (Oct. 14-20 poll)

* Voting for Democratic challenger Cal Cunningham: 47%

* Voting for Republican Senator Thom Tillis: 47%

* Cunningham led Tillis 46%-42% in the prior week.

* 12% said they had already voted.

MICHIGAN (Oct. 14-20 poll)

* Voting for Democratic Senator Gary Peters: 50%

* Voting for Republican challenger John James: 45%

* Peters led James 52%-44% in the prior week.

* 28% said they had already voted.

ARIZONA (Oct. 7-14 poll)

* Voting for Democratic challenger and former astronaut Mark Kelly: 52%

* Voting for Republican Senator Martha McSally: 41%

* Kelly was up 51%-41% in the prior poll.

* 10% said they had already voted.

NOTES: The Reuters/Ipsos poll was conducted online and in English. The Michigan poll surveyed 686 likely voters and had a credibility interval of 4 percentage points. North Carolina's surveyed 660 likely voters and had a credibility interval of 4 percentage points. The earlier Arizona survey included 667 likely voters and had a credibility interval of 4 percentage points.

(Reporting by Jason Lange; Editing by Scott Malone and Cynthia Osterman)