Obviously if the employer actually cares about your credit "rating" and you don't have a good one, that employer will not hire you.

However, many employers are actually checking something else (not your credit "score" - which I'm not even sure they obtain on the reports designed for prospective employers) when they "check your credit."

What you should do is make certain that the three major credit reporting agencies have your personal info correct (e.g. past and present residence addresses and past/present employers), and that they all say the same thing that your resume says. 

If an employer checks your credit report and finds 2 or 3 different employers and several addresses in different states, none of which appear on your resume -- that could be more of a problem than whether your credit "score" is 500 or 600 or 700 or 800 or whatever.

Also, believe me, it is QUITE possible to tell the difference between an individual who basically had decent credit but hit a rough spot (perhaps due to a business failure or a period of unemployment which presumably has already been disclosed to the new prospective employer), and an individual that has a LOOOONG history stretching back as far as the agency is allowed to report of repeated defaults, collection accounts, write-offs,  judgments, evictions, repos, foreclosures, etc., etc., etc., etc., which (presumably) would be more off-putting to a prospective employer than a few recent late-payments on the part of an individual whom they already know has been laid off for the past several months (or whatever).

Also, some employers are reluctant to hire employees with extremely high debt:income ratios into positions in which the prospective employee could be bribed or blackmailed, or in which the employee may have too many ready opportunities to steal or embezzle or otherwise misappropriate the employer's assets.

If that describes you (e.g., $170,000 of unsecured credit card debts and another $450,000 of unpaid medical bills, plus a mortgage company that has commenced foreclosure proceedings, and a bank that is trying to repo your main ride, etc.) it is probably pretty likely that you won't get a job right now managing a company's multi-zillion dollar International financial transactions, no matter how unfair that might seem or no matter how good a reason you might have for your current financial difficulties.  

For positions in which the company (rightfully) does need to be worried about your susceptibility to blackmail or bribes or temptation to embezzle ... you may just have to wait a few years until your own personal finances are back on solid ground before you will be eligible for such positions.

But there are TONS of other positions in which most companies basically Don't Care how wretched your credit report is.  The reason they ask your permission to obtain a credit report is because they hire background checking agencies that obtain your credit report as part of a comprehensive package (also including info about criminal and civil court proceedings against you, tax liens and liabilities, licenses and business registrations, driving record, etc.) - but in order to (legally) get that whole package they have to specifically obtain your permission to check your credit report.  Most of the time they don't really care about your credit report, per se.