WASHINGTON (AP) -- Democratic candidates in several pivotal Senate races are raising more money than their GOP counterparts, but they'll need the cushion to counter spending by independent conservative groups determined to win a Republican majority.

Democrats outraised Republicans in seven of 10 key races in the April-June period, according to quarterly reports that had to be filed by midnight Sunday with the Federal Election Commission.

In Hawaii, New Mexico and North Dakota, GOP candidates had a fundraising edge.

Democrats say an edge is important because outside groups are investing heavily in an effort to win a Republican majority.

For example, American Crossroads and its affiliate, Crossroads GPS, plans on spending up to $70 million supporting Republican Senate candidates in the fall.