Washington (CNN) A new national poll of Republican voters shows Donald Trump continues to lead the race for the GOP presidential nomination, but the margin is tightening in the face of an onslaught of attacks and a smaller GOP field.

Texas Sen. Ted Cruz has gained on the front-runner since January and stands ahead of Florida Sen. Marco Rubio and Ohio Gov. John Kasich.

The ABC/Washington Post poll released Tuesday finds Trump with 34% support, followed by Cruz with 25%. Rubio is No. 3 with 18% support, ahead of Kasich at 13%.

The new numbers reflect a slight tightening of the race, since establishment Republicans have come out swinging against Trump with attack ads and public condemnations. An ABC/Washington Post GOP national poll in January showed Trump ahead of Cruz 37% to 21%. Rubio has also gained 7 points since then, and Kasich has surged 11 points from 2% at that time, as the Republican field has winnowed.

The poll also tested hypothetical match-ups between Trump and Cruz and Trump and Rubio, and found the front-runner losing those contests. The polling could potentially provide some hope to establishment Republicans eager for signs of vulnerability on Trump's part, and fueling arguments for consolidation in the GOP race behind a single Trump challenger.

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