A Quinnipiac University Swing State Poll shows Democrat Hillary Clinton falling behind Republican Rand Paul in Iowa.

Clinton's decline is showing in three critical swing states — Colorado, Iowa and Virginia, the poll finds. She is tied with every Republican candidate in the key state of Iowa.

The Iowa caucuses are the first major electoral event of the nominating process for president.

The poll "numbers are a boost for U.S. Sen. Rand Paul of Kentucky as he formally launches his campaign," said Peter A. Brown, assistant director of the Quinnipiac University Poll.

"Ominous for Hillary Clinton is the broad scope of the movement today compared to her showing in Quinnipiac University's mid-February survey. It isn't just one or two Republicans who are stepping up; it's virtually the entire GOP field that is running better against her.