Story highlights The list of contenders Clinton is seriously weighing is believed to be fewer than five

Clinton is leaning toward announcing her decision immediately after the Republican convention ends

Washington (CNN) Hillary Clinton is spending a rare day away from the campaign trail and the fundraising circuit, arriving at her Washington home on Thursday to pore through reams of research about potential running mates before she begins a final series of interviews and appearances with her top vice presidential choices.

The list of contenders Clinton is seriously weighing is believed to be fewer than five, several Democrats familiar with the process say, and all contenders are not on equal footing. She has a preferred candidate or two in mind, CNN has learned, but intends to keep her options open until Donald Trump reveals his selection.

Clinton is leaning toward announcing her decision immediately after the Republican convention ends on July 21. But aides say she is leaving open the possibility of waiting until Democrats are already gathering for their convention in Philadelphia the following week to disclose her selection, hoping to stoke drama and build interest in the Democratic ticket.

Cheryl Mills, a longtime confidant who is taking a lead role in the vetting process, walked into Clinton's residence in Northwest Washington on Thursday morning. James Hamilton, a veteran Washington lawyer who is overseeing the teams of lawyers researching the candidates, also was on hand. Clinton arrived less than an hour later and stayed until past sundown.

For nine hours Clinton's home was the site of constant activity, with more than half a dozen cars coming and going from the estate. All the cars were directed by Secret Service agents into the property through the protected driveway, so it was not clear who was inside the vehicles.

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