The Washington, D.C., fundraiser also is benefiting John Callahan of Bethlehem, Penn., and David Cicilline, of Providence, R.I., who are seeking U.S. House seats.
The invitation says it's paid for by a joint fundraising committee authorized by McAdams, Callahan and Cicilline, called Moving Mayors Forward. All three are mayors.
Cicilline faces a primary Tuesday.
Suggested contributions range from $1,000 to $7,200.
McAdams spokeswoman Heather Handyside didn't believe McAdams would attend the event Tuesday. Begich has been helping McAdams, lending staff to his Senate campaign.
McAdams' GOP rival, Joe Miller, is expected in Washington this month for meetings and fundraising.
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