Insurance premiums have quickly become a new front in the Obamacare fight, with opponents pouncing on big increases and supporters and experts countering the increases won't be so bad.

The fight started last month when insurers were required to disclose estimated 2016 rates of 10 percent or more for Obamacare customers. Some figures grabbed headlines, especially with certain insurers calling for 50 to 70 percent increases.

The premium spikes vary by state and insurer. For instance, some plans in Florida are actually proposing reduced premiums, but 13 plans want rate increases of 10 percent or more, including Time Insurance Co.'s 63 percent hike.

Republicans say the higher rates are evidence that the law is hurting Americans and not lowering healthcare costs.

"The whole point of Obamacare was to make health care more affordable. But premiums aren't going down; they're going up — way up," said Rep. Paul Ryan, R-Wis., chairman of the House Ways and Means Committee, in a recent hearing.

"The model we're on in the Affordable Care Act is not sustainable," said Rep. Mike Kelly, R-Pa., at the same hearing.

This is the first time since Obamacare's passage that insurers can look at a full year's worth of claims data and calculate premiums, Rep. Pete Roskam, R-Ill., said at the hearing. He added that the premium spikes are not growing pains.

"The law created a number of temporary programs to pay out billions in taxpayer funds during the first few years to lower costs seen by individuals and to protect big insurance companies against financial losses," he said. "But those programs are beginning to phase out, and as the government is slowly taking off the training wheels, Obamacare is looking pretty wobbly."

Supporters counter that any increases aren't finalized and will have a modest impact overall.

"We have just the bad news," said Kathy Hempstead, who directs coverage issues for the Robert Wood Johnson Foundation.

One analysis found that Obamacare customers as a whole may only see a modest increase.

The research firm Avalere looked at proposed rate filings in seven states and the District of Columbia. The average premiums for silver plans, the second cheapest option and a popular choice for Obamacare enrollees, will increase nearly 6 percent, Avalere said.

Avalere also noted that the low-cost silver plan options are likely to be smaller than the silver plan as a whole. Premiums for the lowest- and second-lowest silver plans in the seven states and D.C. will increase on average 4.5 percent and 1 percent.

A separate analysis from the nonpartisan Kaiser Family Foundation found that in 11 major cities the cost of a regular silver plan would be on average 4.4 percent higher in 2016 than this year.

Premiums must be finalized by October. That way customers facing a high premium can choose a different plan during the next open enrollment this fall.

Another reason why the rates could change is states need to conduct reviews themselves.

Obamacare requires states to report on any premium increase trends and recommend whether certain plans should be excluded from the exchanges, according to the National Conference on State Legislatures.

In 2011, the federal government started to work with states to strengthen or alter their rate review programs. If a state doesn't have the resources to conduct the required review, the Department of Health and Human Services will do it, the National Conference on State Legislatures said.

"The carriers really have to be able to explain their rates, and that is part of the point of the whole medical loss-ratio regulations," Hempstead said.

The medical loss ratio is another new regulation installed under Obamacare. It requires insurers to devote 85 percent of the cost of a premium on medical care and the other 15 percent on administrative costs.

The ratio ensures that insurers don't devote too much of their costs to overhead.

Amid the rhetoric over the premium increases are certain trends that could affect the insurance market as a whole.

Many Blue Cross Blue Shield insurers kept premiums in marketplaces comparatively low with small increases from year to year, but that varies considerably across the country, according to a study of trends for market place plans done by the foundation and the left-leaning think tank Urban Institute.

The report looked at the cheapest silver plans in 30 states. Some insurance companies were reluctant to enter the Obamacare marketplaces in 2014 and when they did the plans were more expensive.

However, the report projects insurers will lower premiums to keep prices low to attract enough customers buying insurance through the Obamacare marketplaces.

But for opponents of Obamacare, the proposed increases represent a long-standing criticism about the law's ability to battle healthcare costs, which was levied even before the exchanges opened in 2014.