The basket should not clear on a failed credit card charge, but the checkout manager must save an invoice prior to doing any operation with a payment provider since, in many cases the gateway wants the invoice number.

In order to do a retry payment, you should get the invoice from the IPaymentResult returned from the first attempt ... if it failed:

 var attempt = checkoutManager.Payment.AuthorizeCapture( ...
 if (!attempt.Payment.Success) 
 {
       // basket should still contain items

       // log the failure           

       // for retry we need the user to correct the CC number
       // so we need to get it from them

       // make sure the invoice key is returned to you retry 
       // note: it should be since it's in the IPaymentResult
        // e.g.    var invoice = attempt.Invoice;
        //            var invoiceKey = invoice.Key;

       // or async JS
       var result = new { success: false, invoiceKey: invoice.Key.ToString(), translatedErrors: myPaymentErrorTransaltor(attempt.Payment.Exception.Message)  };

       // redirect or async JS response with appropriate value
       return [some ActionResult]
 }
 else
 {
     // SUCCESS
     // basket should be empty if the default CheckoutContxt 
     // setting is left true (this is configurable**) 

      CustomerContext.SetValue("invoiceKey", invoiceKey.ToString());

     // redirect to receipt 
 }

In the retry controller method

  var paymentMethodKey = [method parameter?]
  var invoiceKey = [method parameter?];
  var invoice = invoiceService.GetByKey(invoiceKey);

  if (invoice != null) 
  {
        var retryAttempt = invoice.CapturePayment(...

        if (!retryAttempt.Payment.Success) 
        {
              // basket should still be populated

              // repeat retry process
        }
        else
        {
              // basket should be empty (depending on CheckoutManager CheckoutContext setting)


             CustomerContext.SetValue("invoiceKey", invoiceKey.ToString());

              // redirect to receipt
        }
  }

** You can set the basket to not clear through the CheckoutManagers CheckoutContext setting EmptyBasketOnPaymentSuccess - set this to false and you'll have to empty it manually.

Unless you are comfortable with the inner workings of the CheckoutManager, It's a probably a good idea to make certain you are using the SAME settings each time you instantiate the CheckoutManager throughout the entire Checkout or you may get results you don't expect =)

You can set the default values in the merchello.config file

   <checkoutContextSettings>
      <setting alias="InvoiceNumberPrefix" value="FT" />
      <setting alias="ApplyTaxesToInvoice" value="true" />
      <setting alias="RaiseCustomerEvents" value="false" />
      <setting alias="ResetCustomerManagerDataOnVersionChange" value="false" />
      <setting alias="ResetPaymentManagerDataOnVersionChange" value="true" />
      <setting alias="ResetExtendedManagerDataOnVersionChange" value="true" />
      <setting alias="ResetShippingManagerDataOnVersionChange" value="true" />
      <setting alias="ResetOfferManagerDataOnVersionChange" value="true" />
      <setting alias="EmptyBasketOnPaymentSuccess" value="true" />
</checkoutContextSettings>