A new poll from Rasmussen may foreshadow a tough primary fight down the road for Republican Sen. John McCain (Ariz.) in 2010.

In a hypothetical match-up against former Rep. J.D. Hayworth, who is reportedly considering a 2010 bid, McCain holds only a two-point lead, besting his potential opponent 45 percent to 43, according to Rasmussen.

That means Hayworth is already polling within the margin of error — a tough spot for any incumbent to be in, especially one who formerly won his party's presidential nomination.

Nevertheless, Rasmussen is quick to point out that the winner of the GOP primary could sail through the general election, as Democrats are still without a strong candidate.