On June 1, 2010, he won the Republican primary without any serious challengers.

And with the Heat now a serious challenger in the division, the life of Riley is still good.

And it seemed to work: in the early polls Labor looked to be a serious challenger.

Others were raising money for 2008, hoping that a fat campaign war chest would discourage serious challengers.

Ms. Montgomery has not had a serious challenger in years.

The Australian team was considered the most serious challenger to their prospects.

His re-election bid did not draw one single serious challenger.

We haven't used this program yet, but those who have say it is a serious challenger to 1-2-3.

So, too, was the presence of a serious challenger rather than another stalking horse.

The surprisingly close race, however, indicated that Feeney could be brought down with a serious challenger.