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In a surprise move, the cities of Las Vegas and Cincinnati withdrew their bids to host the 2016 Republican National Convention on Thursday, RNC officials told ABC News.

Until today, Vegas and Cincinnati were among the cities under consideration to host the quadrennial convention, and many believed Vegas to be the front-runner. Now just four contenders remain:

• Cleveland
• Dallas
• Denver
• Kansas City, Mo.

According to two RNC officials: "Vegas sent a letter withdrawing their bid for national convention based on our criteria for the arena facility and enough onside prep time. Cincinnati did as well."

News of Cincinnati's withdrawal was first reported by the Cincinnati Enquirer, and the Las Vegas announcement was first reported first by Nevada reporter Jon Ralston:

Vegas withdrew for two reasons: No guarantee an arena would be ready in time, and no guarantee of money behind it. Dallas has $25M. 2/2

- Jon Ralston (@RalstonReports) May 22, 2014

Over the last few months, RNC staffers have been visiting the potential host cities to evaluate venues, hotels and financing. Two cities - Phoenix and Columbus, Ohio - were eliminated in early April after what the RNC called "a painstaking review."

The remaining cities are jockeying to host what is usually the coronation ceremony for the party's 2016 presidential nominee. The huge event requires immense planning, but can also give a boost a city's local economy.

ABC's Ryan Struyk contributed reporting.