You did see what happened to the markets around the world when there was the thought that Greece might default on their debt, right?
If the US defaults, you'll have another Great Recession all over again - and probably worse.
And Republicans will get blamed for it, because they are the ones trying to conditionalize the debt ceiling bill.
The taxes and spending should be tied to one another in negotiations. The debt ceiling should be passed and done so promptly.
August 3rd is when millions of seniors are supposed to get their Social Security checks. If they don't get them, it will be VERY easy to pin this on Republicans - who are already in trouble with seniors over the Ryan budget.
Government shutdowns are almost always blamed on Republicans, because Republicans are anti-government.