A new FOX News poll shows Republican Donald Trump leading Ted Cruz by 18 points, while Democrat Hillary Clinton now only has a two-point lead over Bernie Sanders.

FOX's Rachel Sutherland has more details from Washington:

Voters polled believe Donald Trump has the best chance of beating Hillary Clinton this fall, but they don't think he's the right person to negotiate with Russian President Vladamir Putin, Clinton fits that bill instead.

65% of Republicans think Trump has the knowledge to effectively serve as President, while only 12% of Democrats do.

Voters see two nomination battles of strikingly different character. Eight in 10 say the Republican campaign is "rude and disrespectful", while most think the Democratic side is "polite and respectful".

The poll also shows the economy is the top issue on voters' minds.

In Washington, Rachel Sutherland, FOX News.